In bookbinding installations considerable operating difficulties are usually encountered in the correct conveyance of the signatures to subsequent machines provided for further treatment or for the binding of the signatures themselves. Although apparatus for transferring the various signatures from one operating machine to another is known, these operate by taking them from stacks in which the signatures themselves are closely adjacent, in an almost vertical aspect, and disposing them in a horizontal partially accumulated orientation, and such apparatus is structurally rather complex and not completely reliable because of the necessity of taking each individual signature one at a time from the stack of signatures. This conventional apparatus, moreover, does not permit the relative distance of the mutually overlapped signatures conveyed on the horizontal output conveyor thereof to be correctly regulated to supply binding machines in dependence on the operating requirements of the machines themselves.